Firearms are used for many purposes, including hunting, protection, and law enforcement. Spent projectiles, bullets, or fragments of bullets often incorporate lead and typically remain in the environment. Projectiles containing lead pose special hazards including lead contamination of water bodies and lead fumes due to the high temperatures experienced by the projectile during the combustion of the propellant. Additionally, due to the high density of lead, cartridges loaded with heavy lead bullets typically have high recoil and pose dangers from over-penetration and ricochets.
As a result, there have been numerous attempts to develop lead-free projectiles for use with firearms, but these efforts to date have met with limited success. Most lead-free projectiles are designed to approximate the weight of lead projectiles to also approximate the energy levels or impact of lead or lead-core projectiles, at similar velocities. The manufacturing process for such projectiles typically includes encapsulating a soft material into a harder jacket to prevent disintegration of the projectile, or fusing powders, often with a polymer or binder substance.
Additionally, due to the intense heat generated by the combusting propellant, the lead-free projectile, typically a thermoplastic polymer, softens or melts. This leads to deposition of the polymer within the barrel of the firearm and poor performance of the projectile.
U.S. Pat. No. 5,399,187 discloses a bullet that is formed from tungsten or a tungsten alloy and certain polymers. Other bullets use a core of polyethylene and iron, bismuth alloys, tin, bonded powders, and/or polymers.
U.S. Pat. No. 4,517,898 and U.S. Pat. No. 5,012,743 attempt to address certain problems of flight by using long cylinder sections and a long overall length. Additionally, these patents are not monolithic in nature because they use metal jacketing to protect a softer polymeric material and to prevent breakup of the projectile.
U.S. Pat. No. 3,902,683 to Bilsbury describes a plastic bullet for target practice, but it is a multicomponent projectile and is designed to break apart on impact. Additionally, because the projectile is made of polyethylene, nylon, or polyvinylchloride, the material softens and deposits in the barrel of the firearm.
U.S. Pat. No. 5,214,237 to McArthur describes a PTFE bullet with numerous aerodynamic features that reduce the velocity and the flight distance of the projectile. The projectile of McArthur is described as being constructed of pure PTFE and is not, therefore, a composite, as the term is used herein.
As a result, a lead-free polymer composite projectile that could be manufactured with a relatively low weight, low recoil, acceptable accuracy, controlled penetration, high energy transfer at impact, and efficient production methods would be useful.